Methods for managing electrical power

ABSTRACT

Certain exemplary embodiments comprise a system comprising a plurality of Active Front End units adapted to be electrically coupled to a direct current (DC) bus. Each of the plurality of Active Front End units can be adapted to be electrically coupled to a separate winding of a transformer of a plurality of transformers. Each of the plurality of Active Front End units can be adapted to convert alternating current (AC) voltage to a DC voltage. Each of the plurality of Active Front End units can be adapted to supply the DC voltage to the DC bus. The DC bus can be adapted to be electrically coupled to a plurality of inverters.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to, and incorporates by referenceherein in its entirety, pending U.S. Provisional Patent Application Ser.No. 60/609,764 (Attorney Docket No. 2004P15695US), filed 14 Sep. 2004.

BACKGROUND

Harmonic distortion can occur when switching a power device in acircuit. For example, harmonic distortion can occur in circuitsproviding power to a motor comprised in a machine.

Electrical systems associated with the machine can comprise motorcontrols, and other high powered electrical systems (e.g., above 2 MW).In particular, the machine can comprise Active Front End units, whichcan also be referred to as Self-Commutating Rectifiers. In certainelectrical systems, Active Front End units (AFE's) can convertalternating current (AC) to direct current (DC). The Active Front Endunits can be switched at a pre-determined rate. The switching of thesecurrents can result in current harmonics in an AC circuit providingpower to the Active Front End units.

Conventional systems and methods can attempt to resist and/or correctharmonic distortion by filtering current on an AC bus. Theseconventional systems and methods can comprise large static filters,which can be relatively costly and inefficient. Conventional systems canoccupy excessive space in a circuit. Additionally, filters can be sizedfor external loads. Also, transformer phase shifting can occur whenutilizing a conventional system and method. Hence, a system and methodfor a managing electrical power and/or resisting harmonic distortion isdisclosed.

SUMMARY

Certain exemplary embodiments can comprise a system adapted to manageelectrical power, such as by resisting harmonic distortion whilesupplying power to an AC motor. The system can comprise a plurality ofActive Front End units adapted to be electrically coupled to a directcurrent (DC) bus. Each of the plurality of Active Front End units can beadapted to be electrically coupled to a predetermined distinct windingof a transformer of one or more transformers. Each of the plurality ofActive Front End units can be adapted to convert alternating current(AC) to DC. Each of the plurality of Active Front End units can beadapted to rectify an AC voltage to a DC voltage and to supply the DCvoltage to the DC bus. The DC bus can be adapted to be electricallycoupled to an inverter adapted to provide power to the AC motor.

BRIEF DESCRIPTION OF THE DRAWINGS

A wide variety of potential embodiments will be more readily understoodthrough the following detailed description of certain exemplaryembodiments, with reference to the accompanying exemplary drawings inwhich:

FIG. 1 is a side view of an exemplary embodiment of a machine 1000;

FIG. 2 is a block diagram of an exemplary embodiment of a machineelectrical system 2000;

FIG. 3 is a schematic diagram of an exemplary embodiment of a system3000;

FIG. 4 is a flowchart of an exemplary embodiment of a method 4000; and

FIG. 5 is a block diagram of an exemplary embodiment of an informationdevice 5000.

DEFINITIONS

When the following terms are used substantively herein, the accompanyingdefinitions apply:

-   -   a—at least one.    -   Active Front End unit—a self-commutated, actively controlled        line converter; a self-commutated infeed/regenerative feedback        unit adapted to convert an alternating current to a direct        current.    -   activity—an action, act, step, and/or process or portion        thereof.    -   adapted to—made suitable or fit for a specific use or situation.    -   alternating current (AC)—an electric current that reverses        direction in a circuit at regular intervals.    -   apparatus—an appliance or device for a particular purpose.    -   apply—put into service.    -   associated with—related to.    -   asynchronous motor—a rotating device powered by electricity        wherein phase differences between three phases of an electrical        supply create a rotating electromagnetic field in the device.        The device comprises a rotor and a stator. Through        electromagnetic induction, the rotating magnetic field induces a        current in stator windings, which in turn sets up a        counterbalancing magnetic field that causes the rotor to turn in        the direction the field is rotating. The rotor rotates slower        than the rotating magnetic field produced by the electrical        supply.    -   automatically—performed via an information device in a manner        essentially independent of influence or control by a user.    -   below—less than.    -   bus—an electrical conductor adapted to transfer electrical        energy.    -   calculating—determining via mathematics and/or logical rules.    -   can—is capable of, in at least some embodiments.    -   change—to cause a difference to occur.    -   closest—most nearly.    -   communicate—to exchange information.    -   communicative coupling—linking in a manner that facilitates        communications.    -   comparing—examining in order to note similarities or differences        between at least two items.    -   comprising—including but not limited to.    -   control—direct, exercise influence over.    -   convert—change.    -   data—distinct pieces of information, usually formatted in a        special or predetermined way and/or organized to express        concepts.    -   define—to establish the outline, form, or structure of.    -   detect—sense or perceive.    -   determination—decision.    -   determining—deciding.    -   device—a machine, manufacture, and/or collection thereof.    -   Direct Current (DC)—a non-alternating electric current.    -   directly—without anything intervening.    -   distinct—distinguishable from others.    -   dragline-mining machine—a large excavation machine used in        surface mining to remove overburden (layers of rock and soil). A        typical dragline casts a wire rope-hung bucket a considerable        distance, collects the dug material by pulling (dragging) the        bucket toward itself on the ground with a second wire rope (or        chain), elevates the bucket, and dumps the material on a spoil        bank, in a hopper, and/or on a pile, etc.    -   drive—a means by which power is transmitted.    -   duty cycle—a fraction of time a system is actually employed in        performing a function; a percentage of time a DC voltage is        substantially non-zero.    -   electrical motor—a motion-imparting device powered by        electricity.    -   electrical—pertaining to electricity.    -   electrically coupled—connected in a manner adapted to transfer        electrical energy.    -   energized—supplied with an electrical current.    -   event—an occurrence.    -   execute—run a computer program or instruction.    -   field exciter—a device adapted to start a synchronous motor.    -   finding—determining.    -   fixed—substantially unchanged over a time period.    -   fixed rate—a frequency of occurrence substantially unchanging        with time.    -   harmonic distortion—for an AC power signal, the ratio of a sum        of the powers of all harmonic frequencies above and/or below a        fundamental current frequency to the power of the fundamental        current frequency.    -   hoist—a system comprising motor adapted to at least vertically        move a bucket of a dragline-mining machine.    -   identify—determine.    -   individually—of or relating to a distinct entity.    -   inductors—a device adapted to induce current in an electrical        circuit via a changing magnetic flux.    -   information—data that has been organized to express concepts. It        is generally possible to automate certain tasks involving the        management, organization, transformation, and/or presentation of        information.    -   information device—any device capable of processing information,        such as any general purpose and/or special purpose computer,        such as a personal computer, workstation, server, minicomputer,        mainframe, supercomputer, computer terminal, laptop, wearable        computer, and/or Personal Digital Assistant (PDA), mobile        terminal, Bluetooth device, communicator, “smart” phone (such as        a Treo-like device), messaging service (e.g., Blackberry)        receiver, pager, facsimile, cellular telephone, a traditional        telephone, telephonic device, a programmed microprocessor or        microcontroller and/or peripheral integrated circuit elements,        an ASIC or other integrated circuit, a hardware electronic logic        circuit such as a discrete element circuit, and/or a        programmable logic device such as a PLD, PLA, FPGA, or PAL, or        the like, etc. In general any device on which resides a finite        state machine capable of implementing at least a portion of a        method, structure, and/or or graphical user interface described        herein may be used as an information device. An information        device can comprise well-known components such as one or more        network interfaces, one or more processors, one or more memories        containing instructions, and/or one or more input/output (I/O)        devices, one or more user interfaces coupled to an I/O device,        etc.    -   input/output (I/O) device—any sensory-oriented input and/or        output device, such as an audio, visual, haptic, olfactory,        and/or taste-oriented device, including, for example, a monitor,        display, projector, overhead display, keyboard, keypad, mouse,        trackball, joystick, gamepad, wheel, touchpad, touch panel,        pointing device, microphone, speaker, video camera, camera,        scanner, printer, haptic device, vibrator, tactile simulator,        and/or tactile pad, potentially including a port to which an I/O        device can be attached or connected.    -   instructions—directions adapted to perform a particular        operation or function.    -   Insulating Gate Bipolar Transistor (IGBT)—a power semiconductor        device that has identical operation to a bipolar transistor, but        has a field effect type gate, so that a gate-emitter voltage is        applied to make it conductive, no current needs to be injected.        When gate-emitter voltage is very low the device switches off.        The commutations are typically faster than with a bipolar        transistor and typically a little slower than with a MOSFET.    -   inverter—a device that converts DC power to AC power or AC power        to DC power.    -   machine readable medium—a physical structure from which a        machine can obtain data and/or information. Examples include a        memory, punch cards, etc.    -   managing—controlling.    -   manually—substantially without assistance of an information        device.    -   may—is allowed to, in at least some embodiments.    -   measure—characterize by physically sensing.    -   measurement—a value of a variable, the value determined by        manual and/or automatic observation.    -   memory device—an apparatus capable of storing analog or digital        information, such as instructions and/or data. Examples include        a non-volatile memory, volatile memory, Random Access Memory,        RAM, Read Only Memory, ROM, flash memory, magnetic media, a hard        disk, a floppy disk, a magnetic tape, an optical media, an        optical disk, a compact disk, a CD, a digital versatile disk, a        DVD, and/or a raid array, etc. The memory device can be coupled        to a processor and/or can store instructions adapted to be        executed by processor, such as according to an embodiment        disclosed herein.    -   method—a process, procedure, and/or collection of related        activities for accomplishing something.    -   mine—an excavation in the earth from which materials can be        extracted.    -   network—a communicatively coupled plurality of nodes.    -   network interface—any device, system, or subsystem capable of        coupling an information device to a network. For example, a        network interface can be a telephone, cellular phone, cellular        modem, telephone data modem, fax modem, wireless transceiver,        ethernet card, cable modem, digital subscriber line interface,        bridge, hub, router, or other similar device.    -   obtain—to acquire, get, receive, calculate, and/or determine.    -   operational—in service.    -   operator—an entity able to control a machine.    -   optimizing—improving.    -   parameter—a sensed, measured, and/or calculated value.    -   phase angle—an angle expressing a phase relation between an AC        current and an AC voltage.    -   plurality—the state of being plural and/or more than one.    -   power—a measure of energy and/or work.    -   power events—power affecting changes in voltage and/or current.    -   predetermined—established in advance.    -   predetermined threshold—a standard established in advance.    -   pre-set—established in advance.    -   processor—a device and/or set of machine-readable instructions        for performing one or more predetermined tasks. A processor can        comprise any one or a combination of hardware, firmware, and/or        software. A processor can utilize mechanical, pneumatic,        hydraulic, electrical, magnetic, optical, informational,        chemical, and/or biological principles, signals, and/or inputs        to perform the task(s). In certain embodiments, a processor can        act upon information by manipulating, analyzing, modifying,        converting, transmitting the information for use by an        executable procedure and/or an information device, and/or        routing the information to an output device. A processor can        function as a central processing unit, local controller; remote        controller, parallel controller, and/or distributed controller,        etc. Unless stated otherwise, the processor can be a        general-purpose device, such as a microcontroller and/or a        microprocessor, such the Pentium IV series of microprocessor        manufactured by the Intel Corporation of Santa Clara, Calif. In        certain embodiments, the processor can be dedicated purpose        device, such as an Application Specific Integrated Circuit        (ASIC) or a Field Programmable Gate Array (FPGA) that has been        designed to implement in its hardware and/or firmware at least a        part of an embodiment disclosed herein.    -   provide—supply.    -   range—an amount or extent of variation.    -   rate—frequency of an occurrence.    -   reactive AC current—a measure a vectorial and/or imaginary        component of an alternating current not adapted to perform work.    -   related—associated with.    -   remaining—not activated in a present cycle.    -   rendered—made perceptible to a human. For example data,        commands, text, graphics, audio, video, animation, and/or        hyperlinks, etc. can be rendered. Rendering can be via any        visual and/or audio means, such as via a display, a monitor,        electric paper, an ocular implant, a speaker, and/or a cochlear        implant, etc.    -   resist—to stand and/or act against an action, effect, and/or        force.    -   responsive—reacting to an influence and/or impetus.    -   rotation—an act or process of turning around a center or an        axis.    -   save—retain data in a memory device.    -   secondary winding—a wire coil comprised in a transformer adapted        to receive transferred energy induced from an alternating        current conducted through a primary winding comprised in the        transformer.    -   separate—distinct.    -   sequential—following in time.    -   server—an information device and/or software that provides some        service for other connected information devices via a network.    -   set—a related plurality.    -   stagger angle—a phase angle between times for switching on        Active Front End units.    -   start—begin.    -   starting—beginning rotation from a stationary position.    -   step up—change by an incremental amount.    -   store—to place, hold, and/or retain data, typically in a memory.    -   stored—placed, held, and/or retained in a memory.    -   subsequent—following in time.    -   subset—a set comprised in a larger set.    -   substantially—to a great extent or degree.    -   subsystem—a system that is comprised in a larger system.    -   supply—make available for use.    -   switching—turning on arid/or off.    -   synchronous motor—motor having a speed directly proportional to        the frequency of the alternating-current power that operates it.    -   system—a collection of mechanisms, devices, data, and/or        instructions, the collection designed to perform one or more        specific functions.    -   transformer—a device adaptable to transfer electric energy from        one circuit to another. A transformer can comprise a pair of        multiply wound, inductively coupled wire coils that effect such        a transfer with a change in voltage, current, phase, and/or        other electric characteristic.    -   user—a person interfacing with an information device.    -   user interface—any device for rendering information to a user        and/or requesting information from the user. A user interface        includes at least one of textual, graphical, audio, video,        animation, and/or haptic elements. A textual element can be        provided, for example, by a printer, monitor, display,        projector, etc. A graphical element can be provided, for        example, via a monitor, display, projector, and/or visual        indication device, such as a light, flag, beacon, etc. An audio        element can be provided, for example, via a speaker, microphone,        and/or other sound generating and/or receiving device. A video        element or animation element can be provided, for example, via a        monitor, display, projector, and/or other visual device. A        haptic element can be provided, for example, via a very low        frequency speaker, vibrator, tactile stimulator, tactile pad,        simulator, keyboard, keypad, mouse, trackball, joystick,        gamepad, wheel, touchpad, touch panel, pointing device, and/or        other haptic device, etc. A user interface can include one or        more textual elements such as, for example, one or more letters,        number, symbols, etc. A user interface can include one or more        graphical elements such as, for example, an image, photograph,        drawing, icon, window, title bar, panel, sheet, tab, drawer,        matrix, table, form, calendar, outline view, frame, dialog box,        static text, text box, list, pick list, pop-up list, pull-down        list, menu, tool bar, dock, check box, radio button, hyperlink,        browser, button, control, palette, preview panel, color wheel,        dial, slider, scroll bar, cursor, status bar, stepper, and/or        progress indicator, etc. A textual and/or graphical element can        be used for selecting, programming, adjusting, changing,        specifying, etc. an appearance, background color, background        style, border style, border thickness, foreground color, font,        font style, font size, alignment, line spacing, indent, maximum        data length, validation, query, cursor type, pointer type,        autosizing, position, and/or dimension, etc. A user interface        can include one or more audio elements such as, for example, a        volume control, pitch control, speed control, voice selector,        and/or one or more elements for controlling audio play, speed,        pause, fast forward, reverse, etc. A user interface can include        one or more video elements such as, for example, elements        controlling video play, speed, pause, fast forward, reverse,        zoom-in, zoom-out, rotate, and/or tilt, etc. A user interface        can include one or more animation elements such as, for example,        elements controlling animation play, pause, fast forward,        reverse, zoom-in, zoom-out, rotate, tilt, color, intensity,        speed, frequency, appearance, etc. A user interface can include        one or more haptic elements such as, for example, elements        utilizing tactile stimulus, force, pressure, vibration, motion,        displacement, temperature, etc.    -   value—an assigned or calculated numerical quantity.    -   variable—changeable.    -   voltage—a magnitude of an electrical potential.    -   wave—a disturbance, variation, and/or incident that causes the        transfer electrical energy progressively from point to point in        a medium.    -   waveform—a profile, graph, and/or visual model of variations of        voltage and/or current over time.    -   winding—a coil of wire.    -   within—inside.

DETAILED DESCRIPTION

Certain exemplary embodiments can comprise a system comprising aplurality of Active Front End units adapted to be electrically coupledto a direct current (DC) bus. Each of the plurality of Active Front Endunits can be adapted to be electrically coupled to a separate winding ofa transformer of a plurality of transformers. Each of the plurality ofActive Front End units can be adapted to convert alternating current(AC) voltage to a DC voltage. Each of the plurality of Active Front Endunits can be adapted to supply the DC voltage to the DC bus. The DC buscan be adapted to be electrically coupled to a plurality of inverters.

Certain exemplary embodiments can comprise a method for managing and/orresisting harmonic distortion associated with supplying power to an ACmotor associated with a machine. The method can comprise, responsive toa determination that an electrical variable is not within apredetermined range, automatically switching an Active Front End unit ofa plurality of Active Front End units electrically coupled to a DC bus,the Active Front End unit adapted to apply a DC voltage on the DC bus,the Active Front End unit switched on at a rate with a duty cycle, theActive Front End unit electrically coupled to a transformer winding.

Certain exemplary embodiments comprise excavating machines used inmining operations such as the extraction of coal, iron, copper or otherminerals or materials. Excavating machines can comprise dragline-miningmachines, electric mining shovels, bucket wheel excavators, bore miners,and/or continuous, miners, etc. An excavating machine can comprise amachine compartment providing platform supported for rotation. Forcertain machines, the machine compartment can comprise a boom supportedby cables or lines, which can be held at an angle of inclination bypendants extending from the boom to a gantry mounted on top of themachine compartment. Certain machines can comprise a bucket, which canbe suspended from the boom by hoist ropes wound on hoist drums in themachine compartment. In certain exemplary embodiments, the bucket can bedragged toward the dragline excavating machine by coordinated motion ofhoist ropes drag ropes. Drag ropes can be wound on drums comprised inthe machine compartment. The machine compartment can comprise drivesystems for driving hoist, drag motors, walk motors, and/or “swing”motors. The motors can be adapted to control excavation, rotate themachine compartment and/or to move a particular excavating machine.Power to operate excavating machines can be obtained via alternatingcurrent (AC) utility power lines.

FIG. 1 is a side view of an exemplary embodiment of a machine 1000,which can comprise a machine compartment 1800. Machine 1000 can comprisea boom 1600 projecting upwardly from the lower front of machinecompartment 1800. Boom 1600 can be held at an angle of inclination bymeans of pendants 1550 extending from boom 1600 to a gantry 1300, whichcan be mounted on top of machine compartment 1800. A bucket 1700 can besuspended by hoist ropes 1500 which can pass over a sheave 1450 and windon a hoist drum 1100. Bucket 1700 can be dragged toward the draglineexcavating machine 1000 by drag ropes 1650, which can pass overfairleads 1350 near boom foot pins 1400 and onto drag drums 1200.Machine 1000 can be mounted on a walking shoe or walking mechanism 1900,which can allow the dragline excavating machine to be moved from placeto place.

FIG. 2 is a block diagram of an exemplary embodiment of a machineelectrical system 2000, which can comprise a synchronous hoist motor2100 and/or a synchronous drag motor 2110. In certain exemplaryembodiments, hoist motor 2100 and/or drag motor 2110 can comprise aplurality of winding segments. A powered circuit can be adapted tooperate each of hoist motor 2100 and drag motor 2110 to provide motionfor certain pieces of machinery. For example, Hoist motor 2100 can beadapted to provide motive force to a hoist, such as by turning hoistdrum 1100 of FIG. 1. Drag motor 2110 can be adapted to provide motiveforce for a drag motion such as by providing power to drag drum 1200 ofFIG. 1. Field exciters, such as field exciter 2360 and field exciter2560, can be adapted to start rotation of each of hoist motor 2100 andhoist motor 2110.

Certain exemplary embodiments can comprise a plurality of non-operatingasynchronous three phase motors 2120, each of which can comprise asingle winding segment. System 2000 can comprise a plurality ofoperating asynchronous three phase motors 2130, 2140. Motors 2120, 2130,2140 can be cycled on and off according to needs based upon machinemotion and digging cycles. For example, plurality of asynchronous motors2120, 2130, 2140 can be adapted to provide motive force to transverselymove a machine, such as by driving walking mechanism 1900 of machine1000 of FIG. 1. Asynchronous motors 2120, 2130, 2140 can be adapted toprovide motive force to devices adapted to provide a swinging motion toa boom, such as boom 1600 of machine 1000 of FIG. 1.

To provide power to motors, such as hoist motor 2100 and/or drag motor2110, a plurality of inductors 2380 can step up an AC voltage suppliedvia a primary AC bus 2150 and a plurality of secondary AC buses 2190 viaa plurality of transformers 2200, 2240, 2270. An alternating currentassociated with the AC voltage can be measured at a plurality of currenttransformers 2390, which can be adapted to measure total, active, and/orreactive current values. Each of transformers 2200, 2240, 2270 cancomprise a respective set of primary windings 2210, 2245, 2275.Transformer 2200 can comprise secondary windings 2220, 2230. Transformer2240 can comprise secondary windings 2250, 2260. Transformer 2270 cancomprise secondary windings 2280, 2290. Each of secondary windings 2220,2230, 2250, 2260, 2280, 2290 can be electrically coupled to a pluralityof DC buses 2320, 2420, 2520, 2620. An AC voltage provided viatransformers 2200, 2240, 2270 can be managed and/or rectified by aplurality of Active Front End units 2300, 2400, 2500, 2600 to provideone or more predetermined DC voltages to respective DC buses 2320, 2420,2520, 2620.

In certain exemplary embodiments, for a particular DC bus such as DC bus2320, each of plurality of electrically coupled Active Front End units2300 can receive an AC voltage from a predetermined distinct secondarywinding comprised in plurality of transformers 2200, 2240, 2270.Receiving the AC voltage from predetermined distinct secondary windingscan retard a direct current associated with DC bus 2320 from flowing totransformers 2200, 2240, 2270 as the AC voltage cycles below the DCvoltage of DC bus 2320.

When measurements associated with any of plurality of DC buses 2320,2420, 2520, 2620 are determined not to be within respectivepredetermined ranges, one or more corresponding Active Front End units2300, 2400, 2500, 2600 can apply a voltage to at least one of DC buses2320, 2420, 2520, 2620 and/or can remove power from at least one of DCbuses 2320, 2420, 2520, 2620. For example, when electric motors 2100,2110, 2120, 2130, 2140 operate to generate electrical power, ActiveFront End units can act to feed AC power to AC bus 2150 via transformers2200, 2240, 2270.

DC buses 2320, 2420, 2520, 2620 can be electrically coupled to a DCchopper. For example DC chopper 2560 can be electrically coupled to DCbus 2500. DC chopper 2560 can be adapted to reduce a DC voltageassociated DC bus 2500 responsive to a determination that the DC voltageexceeds a predetermined threshold.

Active Front End unit switching can take place at a rate to regulate DCvoltage values associated with DC buses 2320, 2420, 2520, 2620. Each ofplurality of Active Front End units 2300, 2400, 2500, 2600 can switch onand off at a predetermined frequency and/or variable duty cycle, eitherof which can be based upon the voltage and/or current values and/orwaveforms associated with AC bus 2150 and/or DC buses 2320, 2420, 2520.In certain exemplary embodiments, the predetermined frequency and/orvariable duty cycle can be based upon a programmed need for line VARs.In certain exemplary embodiments, predetermined frequency and variableduty cycle can be based upon a number of Active Front End units and aload from devices electrically comprised in and/or coupled to system2000. Plurality of Active Front End units 2300, 2400, 2500, 2600 can beadapted to provide a relatively quick response to load changes in system2000. In certain exemplary embodiments, plurality of Active Front Endunits 2300, 2400, 2500, 2600 can respond to a load change in system 2000at a rate of 7.5 times a line frequency associated with AC bus 2150. Forexample, for a line frequency of 60 Hz, plurality of Active Front Endunits 2300, 2400, 2500, 2600 can respond to a load change in system 2000in 1/450^(th) of a second.

Each of plurality of Active Front End units 2300, 2400, 2500, 2600 canbe adapted to convert an AC voltage to a DC voltage at a fixed voltagelevel. The DC voltage transferred to DC buses 2320, 2420, 2520, 2620 canbe converted to a variable AC frequency via a plurality of inverters2340, 2440, 2540, 2640. The variable AC frequency can be adapted todrive AC motors and to vary the speed and/or the torque of AC motors.

Harmonic distortion associated with AC bus 2150 can be managed and/orresisted via utilization of a plurality of Active Front End units foreach DC bus. Plurality of Active Front End units 2300, 2400, 2500, 2600electrically coupled to distinct predetermined transformer windings,such as secondary windings 2220, 2240, 2270, can isolate AC bus 2150from feedback associated with switching plurality of Active Front Endunits 2300, 2400, 2500, 2600. Certain exemplary embodiments can comprisea “minimal factor” of Active Front End units. For example, in system2000, eighteen Active Front End units can be associated with hoist motor2100 and drag motor 2110.

Managing and/or resisting harmonic distortion can result in less heatemitted from -transformers 2200, 2240, 2270, a larger K factor fortransformers 2200, 2240, 2270, and/or fewer transformers 2200, 2240,2270 for certain mining machines. In certain exemplary embodiments,transformer sizes can be increased as compared to systems comprisingonly a single Active Front End unit electrically coupled to each DC bus.

In certain exemplary embodiments, a plurality of inverters 2340, 2440,2540, 2640 can be electrically coupled to respective DC buses 2320,2420, 2520, 2620. Each plurality of inverters 2340, 2440, 2540, 2640 canreceive a DC voltage and convert the DC voltage to an AC voltage with apredetermined and/or selectably variable frequency.

Synchronous motors, such as hoist motor 2100 and drag motor 2110, can bethree phase motors and can comprise 3 segments per winding. Asynchronousmotors, such as plurality of asynchronous motors 2120, 2130, 2140, canbe three phase motors and can comprise one segment per winding.Asynchronous motors 2120, 2130, 2140 can be adapted to receive analternating current comprising a variable frequency and variablevoltage.

In an exemplary embodiment of this invention, a method for managingand/or resisting the harmonic distortion can comprise staggering atiming of at least one Active Front End unit of the plurality of ActiveFront End units 2300, 2400, 2500, 2600 via a stagger angle, which can bedetermined by dividing a 360 degree cycle by a quantity of Active FrontEnd units operating and/or electrically coupled to DC buses 2320, 2420,2520, 2620.

The superimposed stagger angle can be determined by dividing 360 degreesby a total quantity of operating Active Front End units comprised insystem 2000. For example, if hoist motor 2100 is operating, but none ofplurality of asynchronous motors 2120, 2130, 2140 are operating, ActiveFront End units coupled to buses 2320, 2420, 2520 providing power tohoist motor 2100 can switch based upon a stagger angle of 20 degrees(=360 degrees÷18 AFE's) relative to at least one other coupled ActiveFront End unit. If neither of hoist motor 2100 and drag motor 2110 areoperating, a stagger angle for at least one of plurality of Active FrontEnd units 2600 coupled to plurality of asynchronous motors 2120, 2130,2140 can be 60 degrees (=360 degrees÷6 AFE's) relative to at least oneother of plurality of Active Front End units 2600. If at least one ofhoist motor 2100 and drag motor 2110 is operating, and at least one ofplurality of asynchronous motors 2120, 2130, 2140 is operating, astagger angle of at least one Active Front End unit of plurality ofActive Front End units 2300, 2400, 2500, 2600 can be switched with asuperimposed stagger angle of 15 degrees (=360 degrees÷24 operatingAFE's).

FIG. 3 is a schematic diagram of an exemplary embodiment of an system3000, which can comprise a source of alternating current 3100. A voltagesensor 3650 can be adapted to measure an AC voltage of alternatingcurrent 3100, such as on an AC bus, on a primary side of a voltagetransformer, and/or on a secondary side of the voltage transformer.Alternating current flowing from source of alternating current 3100 canbe measured via a current transformer 3200, which can be located on aprimary side of a voltage transformer and/or on a secondary side of thevoltage transformer. System 3000 can comprise an inductor 3300, whichcan be adapted to step up an AC voltage fed to transistors 3400, 3500,which can be power switching devices such as IGBT (insulated gatebipolar transistor), IGCT (integrated gate commutated transistors),and/or IEGT (injection enhanced gate transistor) technology, etc.

Transistors 3400, 3500 can be adapted to rectify an AC voltage toprovide a DC voltage to a DC bus 3600. A sensor 3675 can be adapted tomeasure a value of a variable, such as a voltage or a current associatedwith DC bus 3600. Current transformer 3200, voltage sensor 3650, and/orsensor 3675 can be communicatively coupled to an information device3700. Information device 3700 can be adapted to switch transistors 3400,3500 responsive to signals from current transformer 3200 voltage sensor3650, and/or sensor 3675. For example, transistors 3400, 3500 can beswitched on responsive to a voltage value detected by sensor 3675 beingbelow a predetermined threshold. Information device 3700 can change aduty cycle of transistors 3400, 3500 responsive to a provided, obtained,calculated, and/or determined total, active, and/or a reactive currentvalue, a voltage value, such as a voltage measured by voltage sensor3650, and/or an electrical value, such as a voltage and/or a currentmeasured by sensor 3675.

Information device 3700 can be communicatively coupled to a plurality ofinformation devices via network 1900. Network 1900 can be a network thatis public, private, circuit-switched, packet-switched, connection-less,virtual, radio, telephone, POTS, non-POTS, PSTN, non-PSTN, cellular,cable, DSL, satellite, microwave, twisted pair, IEEE 802.03, Ethernet,token ring, local area, wide area, IP, Internet, intranet, wireless,Ultra Wide Band (UWB), Wi-Fi, BlueTooth, Airport, IEEE 802.11, IEEE802.11a, IEEE 802.11b, IEEE 802.11g, X-10, and/or electrical powernetworks, etc., and/or any equivalents thereof. Instructions can beprovided to information device 3700 to switch transistors 3400, 3500 viaan information device communicatively coupled to network 3900.

FIG. 4 is a flowchart of an exemplary embodiment of a method 4000. Atactivity 4100, information can be received regarding electricalinformation measured and/or determined downstream of a plurality ofActive Front End units communicatively coupled to a DC bus associatedwith a machine. For example, information regarding an DC bus voltage, DCbus current, inverter, AC bus voltage, AC bus active current, AC motor,and/or AC total, active, and/or reactive current can be received fromone or more measuring devices.

At activity 4200, a determination can be made that at least one valueregarding the downstream electrical information is not within apredetermined range. For example, a determination can be made that theDC bus voltage is not within a predetermined range.

At activity 4300, information can be received regarding upstreamelectrical circuitry. For example, a voltage and/or current measurementcan be made at an AC bus feeding at least one transformer primarywinding and/or a voltage or current measurement directly related to oneor more of a plurality of AC buses electrically coupled to transformersecondary windings.

At activity 4400, a fixed rate associated with an Active Front End unitcan be determined. In certain exemplary embodiments, the fixed rate canbe determined based upon a stagger angle. The stagger angle can bedetermined by dividing a 360 degree cycle by a number of Active FrontEnd units operating on and/or associated with the machine. The staggerangle can be pre-set to manage pre-calculated AC harmonic distortionsexpected to be caused and/or tested to be caused by predetermined powerevents on the DC bus.

At activity 4500, a variable duty cycle associated with an Active FrontEnd can be determined. In certain exemplary embodiments, a plurality ofvariable duty cycles associated with a plurality of Active Front Endunits can be determined. For example, each variable duty cycle of theplurality of variable duty cycles can be determined based upon a DC busvoltage value. Each variable duty cycle of the plurality of variableduty cycles can be associated with a predetermined Active Front Endunit. In certain exemplary embodiments, each variable duty cycle of theplurality of variable duty cycles can be the same for each of theplurality of Active Front End units for a particular time interval. Incertain exemplary embodiments, each variable duty cycle of the pluralityof variable duty cycles can be distinct for one or more of the pluralityof Active Front End units for a particular time interval. In certainexemplary embodiments, one or more of the plurality of variable dutycycles can be changed to manage a phase angle associated with an ACvoltage and current.

In certain exemplary embodiments, one or more of the plurality ofvariable duty cycles can be determined responsive to a determinationthat a synchronous motor and/or an asynchronous motor associated withthe machine is starting up or shutting down. For example, at least oneof the plurality of duty cycles can be changed responsive to adetermination that a field exciter associated with a synchronous motoris being energized.

At activity 4600, an AC voltage can be rectified to a DC voltage. The DCvoltage can be rectified and applied to the DC bus via an Active FrontEnd unit of a plurality of Active Front End units. Each of the pluralityof Active Front End units can be electrically coupled to the DC bus. TheActive Front End unit can be switched on at the fixed rate with for thevariable duty cycle. The Active Front End unit can be electricallycoupled to a transformer winding, such as a predetermined distincttransformer winding. DC voltages from each of the plurality of ActiveFront End units can be sequentially applied to the DC bus, therebyswitching each of the plurality of Active Front End units during apredetermined time period. Each of the plurality of Active Front Endunits can be switched at a predetermined fixed rate for an automaticallydetermined variable duty cycle.

FIG. 5 is a block diagram of an exemplary embodiment of an informationdevice 5000, which in certain operative embodiments can comprise, forexample, information device 3700 of FIG. 3. Information device 5000 cancomprise any of numerous components, such as for example, one or morenetwork interfaces 5100, one or more processors 5200, one or morememories 5300 containing instructions 5400, one or more input/output(I/O) devices 5500, and/or one or more user interfaces 5600 coupled toI/O device 5500, etc.

In certain exemplary embodiments, via one or more user interfaces 5600,such as a graphical user interface, a user can view a rendering ofinformation related to switching a plurality of Active Front End unitselectrically coupled to a DC bus.

Still other embodiments will become readily apparent to those skilled inthis art from reading the above-recited detailed description anddrawings of certain exemplary embodiments. It should be understood thatnumerous variations, modifications, and additional embodiments arepossible, and accordingly, all such variations, modifications, andembodiments are to be regarded as being within the spirit and scope ofthis application. For example, regardless of the content of any portion(e.g., title, field, background, summary, abstract, drawing figure,etc.) of this application, unless clearly specified to the contrary,such as via an explicit definition, there is no requirement for theinclusion in any claim herein (or of any claim of any applicationclaiming priority hereto) of any particular described or illustratedcharacteristic, function, activity, or element, any particular sequenceof activities, or any particular interrelationship of elements.Moreover, any activity can be repeated, any activity can be performed bymultiple entities, and/or any element can be duplicated. Further, anyactivity or element can be excluded, the sequence of activities canvary, and/or the interrelationship of elements can vary. Accordingly,the descriptions and drawings are to be regarded as illustrative innature, and not as restrictive. Moreover, when any number or range isdescribed herein, unless clearly stated otherwise, that number or rangeis approximate. When any range is described herein, unless clearlystated otherwise, that range includes all values therein and allsubranges therein. Any information in any material (e.g., a UnitedStates patent, United States patent application, book, article, etc.)that has been incorporated by reference herein, is only incorporated byreference to the extent that no conflict exists between such informationand the other statements and drawings set forth herein. In the event ofsuch conflict, including a conflict that would render invalid any claimherein or seeking priority hereto, then any such conflicting informationin such incorporated by reference material is specifically notincorporated by reference herein.

1. A method for managing electrical power in a dragline-mining machine,said method comprising: for a plurality of Active Front End units, eachActive Front End unit from the plurality of Active Front End unitsadapted to be electrically coupled to a DC bus and to apply a DC voltageon the DC bus, each Active Front End unit switched on at a fixed rateand for an individually variable duty cycle, a stagger angle of theplurality of Active Front Ends pre-set to manage AC harmonic distortionscaused by predetermined power events on the DC bus: responsive to adetermination that a voltage measurement on the DC bus is not within afirst predetermined range, automatically changing at least one of theindividually variable duty cycles; and responsive to a determinationthat a phase angle is not within a second predetermined range, the phaseangle calculated from a measured voltage on an AC bus adapted to provideAC power to the plurality of Active Front End units and a measuredcurrent directly associated with a selected Active front End unit fromthe plurality of Active Front End units, automatically changing the dutycycle of at least the selected Active Front End unit.
 2. The method ofclaim 1, further comprising: determining that the voltage value on theDC bus is not within the first predetermined range.
 3. The method ofclaim 1, further comprising: after switching a predetermined ActiveFront End unit, sequentially switching each of a predetermined subset ofthe plurality of Active Front End units electrically coupled to the DCbus, the predetermined subset of Active Front End units not comprisingthe predetermined Active Front End unit, until each of the predeterminedsubset of Active Front End units is switched prior to a subsequentswitching of the predetermined Active Front End unit.
 4. The method ofclaim 1, further comprising: automatically determining the duty cycle ofat least the selected Active Front End unit.
 5. The method of claim 1,further comprising: increasing the duty cycle of at least the selectedActive Front End unit responsive to a determination that an electricalmotor is starting.
 6. The method of claim 1, further comprising:increasing the duty cycle of at least the selected Active Front End unitresponsive to a determination that a synchronous electrical motor isstarting.
 7. The method of claim 1, further comprising: increasing theduty cycle of at least the selected Active Front End unit responsive toa determination that an asynchronous electrical motor is starting. 8.The method of claim 1, further comprising: increasing the duty cycle ofat least the selected Active Front End unit responsive to adetermination that a field exciter is being energized.
 9. The method ofclaim 1, further comprising: determining the duty cycle of at least theselected Active Front End unit based upon a measured DC voltageassociated with the DC bus.
 10. The method of claim 1, furthercomprising: determining the fixed rate based upon a total number ofoperational Active Front End units comprised in the dragline-miningmachine.
 11. The method of claim 1, further comprising: determining thestagger angle.
 12. The method of claim 1, further comprising: obtainingAC current values associated with each of the plurality of Active FrontEnd units electrically coupled to the DC bus.
 13. The method of claim 1,further comprising: calculating the phase angle.
 14. The method of claim1, further comprising: determining the duty cycle of at least theselected Active Front End unit based upon a measured electrical valueassociated with an inverter associated with the dragline-mining machine.15. The method of claim 1, further comprising: determining the dutycycle of at least the selected Active Front End unit based upon ameasured electrical value associated with an electrical motor associatedwith the dragline-mining machine.
 16. The method of claim 1, furthercomprising: receiving instructions adapted to control switching of theplurality of Active Front End units via an information device.
 17. Amethod for managing power in a dragline-mining machine, said methodcomprising: for a first plurality of Active Front End units, each ActiveFront End unit from the first plurality of Active Front End unitsadapted to be electrically coupled to a first DC bus and to apply a DCvoltage on the first DC bus, each Active Front End unit from the firstplurality of Active Front End units switched on at a first fixed rateand for individually variable duty cycles, a first stagger angle of thefirst plurality of Active Front Ends pre-set to manage AC harmonicdistortions caused by predetermined power events on the first DC bus:responsive to a determination that a voltage measurement on the first DCbus is not within a first predetermined range, automatically changing atleast one of the individually variable duty cycles; and responsive to adetermination that a first phase angle is not within a secondpredetermined range, the first phase angle calculated from a measuredvoltage on an AC bus and a measured current directly associated with aselected Active front End unit from the first plurality of Active FrontEnd units, automatically changing the duty cycle of at least theselected Active Front End unit from the first plurality of Active FrontEnd units, the AC bus adapted to provide AC power to the first pluralityof Active Front End units and a second plurality of Active Front Endunits; and for a second plurality of Active Front End units, each ActiveFront End unit from the second plurality of Active Front End unitsadapted to be electrically coupled to a second DC bus and to apply a DCvoltage on the second DC bus, each Active Front End unit from the secondplurality of Active Front End units switched on at a second fixed rateand for individually variable duty cycles, a second stagger angle of thesecond plurality of Active Front Ends pre-set to manage AC harmonicdistortions caused by predetermined power events on the second DC bus:responsive to a determination that a voltage measurement on the secondDC bus is not within a third predetermined range, automatically changingat least one of the individually variable duty cycles; and responsive toa determination that a second phase angle is not within a fourthpredetermined range, the second phase angle calculated from a measuredvoltage on the AC bus and a measured current directly associated with aselected Active front End unit from the second plurality of Active FrontEnd units, automatically changing the duty cycle of at least theselected Active Front End unit from the second plurality of Active FrontEnd units.
 18. A machine-readable medium having stored thereon aplurality of executable instructions, the plurality of instructionscomprising instructions to: for a plurality of Active Front End units,each Active Front End unit from the plurality of Active Front End unitsadapted to be electrically coupled to a DC bus and to apply a DC voltageon the DC bus, each Active Front End unit switched on at a fixed rateand for an individually variable duty cycle, a stagger angle of theplurality of Active Front Ends pre-set to manage AC harmonic distortionscaused by predetermined power events on the DC bus: responsive to adetermination that a voltage measurement on the DC bus is not within afirst predetermined range, automatically changing at least one of theindividually variable duty cycles; and responsive to a determinationthat a phase angle is not within a second predetermined range, the phaseangle calculated from a measured voltage on an AC bus adapted to provideAC power to the plurality of Active Front End units and a measuredcurrent directly associated with a selected Active front End unit fromthe plurality of Active Front End units, automatically changing the dutycycle of at least the selected Active Front End unit.